: The application will examine the mechanism of strand transfer carried out by HIV-1. Specific experiments include examination of the role of RNAse H of the viral RT in the process of transfer. Additionally, the roles of RT in promoting a transfer reaction and the influence of experimental conditions and viral nucleocapsid protein on the reaction will be determined. The investigator will determine the frequency of mutations accompanying homologous versus nonhomologous recombination. Mutations associated with the transfer reaction will be correlated to specific sequence features on the donor template. Examination of strand transfer efficiency and mutagenesis in the presence of Nevirapine will determine whether that drug alters the efficiency of strand transfer in mutagenesis. Drug resistant mutant RT will be used for analysis of strand transfer parameters and mutagenesis. These results will indicate whether drug treatment or drug induced RT mutations can promote or suppress viral recombination.